Process for the production of azelaic acid



PROCESS FOR THE PRODUCTION OF AZELAIC ACID Willi Ziegenbein, Walter Franke, and A'chim Striebeck, Recklinghausen, Germany, assignors to Chemische Werke Hiils Aktiengesellschaft, Marl, Kreis Recklmghausen, Germany, a corporation of Germany No Drawing. Application February 9, 1959 7 Serial N0. 791,811

Claims priority, application Germany September 2, 1958 1 Claim. (Cl. 260-537) The known processes for the production of azelaic acid are based upon the treatment of natural products, from which the acid is obtainable in more or less good yields by saponification and oxidation of the hydrolysis products. Oleic acid and ricinoleic acid yield azelaic acid by ozonization and decomposition of the ozonides. Ricinoleic acid can also be oxidized to azelaic acid by nitric acid. In view of the fact that natural oils are the basis of all of these processes and are mixtures of higher fatty acid esters,-it can be seen that it is difficult to obtain a pure azelaic acid product in this way.

It has been found that it is. possible to produce pure azelaic acid in a complete synthesis by.,condensing 1- methoxy-butene-l-ine-(3) with l-chloro--methoxy-pentene-(2) or -3-chloro-5-methoxy-pentene-(1), or with an isomeric mixture of l-chloro-5-methoxy-pentene*(2) and 3-chloro-S-methoxy-pentene-(1) in an alcoholic solution of an alkali metal hydroxide in the presence of cuprous compounds to form 1,9-dimethoxy-nonadiene-1,6-ine-(3), hydrogenating this in the known manner and oxidizing with nitric acid. The procedural steps are summarized in the following equations:

pentene-(2) which is readily available from butadiene and chloromethylmethylether, or an isomeric mixture of approximately 50-75% of 1-chloro-5-methoxy-pentene-(2) and 50-25% of 3-chloro-methoxy-penteue-(1') obtainable in this manner.

The first step consists in the condensation of 1-methoxyt butene-1-ine-(3) with l-chloro-S-methoxy-pentene-(2) or 3-chloro-5-methoxy-pentene 1) or with an isomeric mixture of l-chloro-5-methoXy-pentene-(2)- and 3-chloro-5- methoxy-pentene (l). The condensation takes place, splitting of hydrogen'chloride, at to 60 C. in alcoholic solution of molar quantities of potassium or sodium hydroxide in the presence of catalytic quantitiesof cuprous chloride, whereby one obtains 1,9-dimethoxymonadiene-l,6-ine-(3) in 65 to 70% yield.

It is not necessary to use pure l-chloro-S-methoxy- "pentene-(2) for the condensation, since 3-chloro-S- methoxy-pentene,-( 1) rearranges under the reaction condi- Patented May- 17, 1960 ice 2 tions and likewise yields 1,9-dimethoxy-nonadiene-1,6-ine- (3). Besides methanol it is also possible to use, ethanol, propanol and dioxan or tetrahydrofuran as the solvent. The addition of cuprous compounds, as for example cuprous chloride, amounts to about 0.55% by weight referred to the methoxy-butenine, After the separation of the alkali metal chloride formed. the 1,9-dimethoxynonadiene-1,6-ine-(3) is recovered by distillation.

In the second stage of the process the l,9-dimethoxynonadiene-1,6-ine-(3) product is hydrogenated. It is not necessary, as described above, to isolate the 1,9-d'imethoxy-nonadiene-1,6-ine-(3) from the reaction mixture, but one can immediately use the solution filtered off from the separated alkali metal chloride from the first step. The addition of hydrogen is carried out in known manner either discontinuously or continuously. For example, the 1,9-dimethoxy-nonadiene-1,6-ine-(3') is treated with hydrogen in a pressure vessel, in the presence of a hydrogen carrier, like Raney nickel, under a pressure of 20 to 2 00 atmospheres and at a temperature between 50 and 150 C. The reaction yields 1,9-dimethoxy-nonane with a yield of more than 90%. a

The last step is the oxidation ofthe 1,9-dimethoxynonane with nitric acid at 20 to 25 C., which yields azelaic acid with 87 to 90% yield, and can be carried out ,advantageously also in the presence of an oxygen carrier,

7 such as vanadium pentoxide.

For the isolation of the azelaic acid the reaction mixture after the oxidation step is diluted with water whereby the acid separates as an almost white crystal mash, which is suction filtered,

washed with water and if necessary recrystallized from more a valuable intermediate product for organic chem ical syntheses.

EXAMPLE the introduction of the 1-chlor0-5-methoxy-pentene-(2) the stirring is continued another 1 to 2 hours, and subsequently the solution is filtered off from the potassium or sodium chloride and the reaction product is distilled under vacuum in a nitrogen atmosphere. At 105 to 108 C. under a pressure of 2 to 3 Torr (150 to 152 C. under v20 Torr) one obtains 560 parts by weight of 1,9-dimethoxy-nonadiene 1,6 --ine (3 (d :0.9572, .n

1.5030) in the form of a pale yellow oil.

(b) Under the same reaction conditions as described under (a) 675 parts by weight of a mixture of about of 1-chloro-5-methoxyfpentene-(2) and 30% of S-chloro- 5-methoxy-pentene-(1)v are reacted with 450 parts by weight of 1-methoxy-butene-1-ine-(3) By distillation between to 108 C. under 2 to 3 Torr one obtains 581 parts by weight of 1,9-dimethoxy-nonadiene,1,6-ine-(3)- in the form ofa pale yellow oil.

(c) If instead of 1-chloro-S-methoxyentene-(Z) there is used 3-ehloro-5-methoxy-pentene-'(,l) in E'xample.1(a),

and if one then proceeds as under 1(a), 1,9-dimethoxynonadiene- 1,6-ine-(3) is obtained in the same yield.

Step 2 SOO'parts by weight of l,9-dimethoxy-nonadiene-1,6- ine-(3) are' hydrogenated in an autoclave under 200 atmospheres of hydrogen pressure in the presence of to parts by weight of Raney nickel. The temperature is maintained for'about 3 hours each at C., C., 110 C.-and 140 C. After filtering off the catalyst sludge one distils under vacuum. Between 121 to 124 C. under 20 Torr. there come over 470 parts by weight of 1,9-dimethoxy-nonane as a colorless liquid (11 0.8553, n 1.4269). 1

= Step 3 Int o parts by weight of fuming nitric acid (D151) to which have been added 0.1 part by weight of vanadium pentoxidejare dropped gradually and with stirring 47 parts 'by weight of 1,9-dimethoxy-nonane. A reaction temperature of 25 C. should not be exceeded. After the introduction of all of the 1,9-dimethoxy-nonane the resulting mixture is allowed to stand for 2 to 3 hours at the same temperature. After stirring the reaction mixture into water the azelaic acid separates out as a crystal mass, which is washed well with water, separated and dried under vacuum. One thus obtains 41.5 parts by weight of the acid wihch is already quite pure (melting point 104 to C.). After recrystallization from hot water and good drying 39.5 partsby weight of a very pure, white azelaic acid with a melting point of 106.5 C. are obtained.

We claim:

Process for the production of azelaic acid which comprises condensing 1-methoxy-butene-1-ine-(3) with a member selected from the group consisting of l-chloro- 5-methoxy-pentene-( 2) 3-chloro-5-n1ethoxy-pentenel and mixtures thereof in an alcoholic solution of an alkali metal hydroxide in the presence of a cuprous compound thereby forming 1,9-dimethoxy-nonadiene-1,6-ine-(3), hydrogenating the latter thereby producing 1,9-dimethoxynonane and oxidizing the latter with nitric acid.

No references cited. 

